Light, Shadows and Reflections:Class 6 Science NCERT Chapter 11
Key Features of NCERT Material for Class 6 Science Chapter 11 – Light,Shadows and Reflection
In the previous chapter 10: Motion And Measurements Of Distances, you have studied about our motion and to calculate the measurements of distances.In this chapter: Light,Shadows And Reflections you will study about the light and the formation of shadows and reflections.
Quick revision notes
Source of light: An article which discharges light, is known as a source of light. For instance, sun, light, and so on.
Non-luminous objects: These are the objects which don’t transmit light of their own. Such a body becomes obvious when light falls on it. For instance, the moon, the planets, and so on.
Ray of light: A straight dainty light emission from a source to an item is known as a ray of light.
Obstacle: An item which goes to the way of the light is called an obstacle.
- Development of a shadow
- All the opaque objects appear to frame their very own dull shadow.
- We need a source of light, an opaque item in the way, and a screen to see a shadow.
- Screen: This is a surface on which the shadow is shaped. It might be a margarine paper or essentially ground.
- Shadows give us some data about states of objects.
- The shade of the opaque article doesn’t influence the shade of the shadow.
- All the space behind the opaque article, up to some separation behind it is by all accounts loaded up with the shadow.
Picture shaped by a pinhole camera
Pictures shaped by a pinhole camera are topsy turvy. Here is an image demonstrating the way of rays of light originating from an article far away to a pinhole and afterward to screen.
At the point when sunlight goes through the leaves of a tree, the holes between the leaves go about as the pinholes. These normal pinholes cast pleasant round pictures of the sun.
Rectilinear propagation: Light goes in an orderly fashion. It is called rectilinear propagation of light.
Picture development by a plane mirror: We can see pictures through a mirror. Picture framed by a mirror (level) has following highlights:
Reflected picture holds the shade of the item.
Picture is erect yet laterally reversed.
Lateral inversion: Right half of the item shows up as left side in the picture shaped by a plane mirror. For instance, on the off chance that we show our correct hand, picture in the mirror will show as left hand.
In a mirror, on the off chance that you see someone else, doubtlessly the other individual can likewise observe you in that mirror.
Luminous: luminous objects give out light of their own.
Mirror: A smooth sparkling surface, which bounce back the light back in same or in various bearings is known as a mirror.
Opaque objects: If an article totally stops the section of all the light falling on it, it is an opaque item.
Pinhole camera: It is a gadget which frames a photo like picture of a brilliant item on a screen.
Impression of light: When a ray of light falls on a smooth and cleaned surface, light returns back in a similar medium. It is called reflection.
Shadow: Opaque objects don’t permit light to go through them and cast dull patches behind them. These dull patches are called shadows.
Translucent objects: Some objects permit just a piece of light falling on them to go through, such objects are called translucent objects. For instance, a solitary dainty piece of paper.
Transparent objects: Those objects which permit all the light to go through them are called transparent objects.
(Chapter:11 Light,Shadows And Reflections)
Sources Of Light
Any article that gives out light is known as a source of light. Luminous objects are likewise called sources of light. Sources of light can be common or counterfeit (man-made)
Instances of normal sources of light are ‘he sun and different steps and bugs like the firefly. Some counterfeit sources of light are flame, electric bulb, and laser.
Transparent, Translucent, And Opaque Materials :
Transparent, Translucent, And Opaque Materials :
Various kinds of materials transmit light in an unexpected way. In light of the manner in which they transmit light, materials can be isolated into transparent, translucent, and opaque materials.
Materials that permit light to go through noteworthy dispersing or assimilation [Fig. 13.2(a)] are called transparent materials. We will have the option to see through these materials obviously. Instances of transparent materials are clear air, clear glass, clean water, a few sorts of plastic, and cellophane paper.
Materials that permit light to go through them, however disperse or diffuse the light as it goes through, i.e., an equal light emission comes through every which way are called translucent materials [Fig. 13.2(b)], That is the reason an article can’t be seen unmistakably through a translucent material. Instances of translucent materials are margarine paper, an off-white glass, paper spread with oil, and smoked glass.
Materials that totally square light are called opaque materials [Fig. 13.2(c)]. We won’t have the option to see through these materials by any means. Instances of an opaque materials are metal, mud, concrete, coal, and wood. A mirror is an excellent case of opaque material. A perfect mirror doesn’t let any light go through it.
(Chapter:11 Light,Shadows And Reflections)
Propagation Of Light
Generally light goes in an orderly fashion. At the point when we need to speak to the propagation of light with a graph, we speak to it with the assistance of rays and bars.
Ray A ray is a line with a bolt that shows the heading of propagation of light, and such a chart is known as a ray graph.
Beam A gathering of light rays moving in a sorted out way is known as a light emission.
The property of light to go in straight lines clarifies many fascinating marvels identified with light, similar to development of shadows by opaque objects and arrangement of pictures in a pin-gap camera.
(Chapter:11 Light,Shadows And Reflections)
Shadows
- An opaque article hinders the light falling on it. This makes a territory of dimness on the item away from the source of light. A translucent item likewise makes a black out region of obscurity. A zone of dimness framed by an opaque article impeding light is known as a shadow. The accompanying three things are required for a shadow to frame (Fig. 13.4):
- a source of light
- an opaque item
- a screen or irface behind the item.
A shadow won’t structure if any of these is missing. This clarifies why we can’t see a shadow in obscurity. It is just when light rays are deterred by an opaque item that we get a sorry excuse for the article.
Let us play out an action to find out about the qualities of a shadow.
Characteristics of a Shadow:
A shadow has the following three characteristics:
- It is black, despite the color of the object that is used to make the shadow
- It only showcases the shape of the object and does not show the details.
- The size of a shadow depends on the distance between the object and the source of light
- It also includes the distance between the object and the screen.
Reflection Surfaces
A shadow has the accompanying three attributes:
It is consistently dark, paying little mind to the shade of the article used to make the shadow
It just shows the shape or diagram of the item and not the subtleties.
The size of a shadow differs relying upon the separation between the item and the source of light, and the separation between the article and the screen.
(Chapter:11 Light,Shadows And Reflections)
Reflection Surfaces
We state light is reflected when it ricochets off a surface. Reflection of light causes us to see the vast majority of the things around us.
Reflection of light by a surface relies upon the idea of the surface. A harsh and uneven surface (likewise called an unpredictable surface) mirrors an equal light emission occurrence upon it in various ways (Fig. 13.5). A genuine case of an unpleasant surface is bark of a tree and cover. This sort of reflection is called diffused reflection.
A smooth surface (a profoundly cleaned surface) mirrors an equal light emission occurrence upon it one way. (Fig. 13.6). A genuine case of a smooth surface is a mirror. At the point when you remain before a mirror, you can see yourself in the mirror. This is called your picture.
An extremely fascinating phenomenon happens when an article frames a picture by reflection. This is something we all more likely than not saw while seeing ourselves in the mirror. At the point when we lift our correct hand, the picture in the mirror seems to lift its left hand. This appearing to be left-right inversion is called lateral inversion.
A picture is unique in relation to a shadow. A portion of the contrasts between a picture and a shadow are given in Table 13.1.
A Pin-hole Camera :
A pin-gap camera is only a crate (Fig. 13.7) with a minuscule gap on one of its sides. Light falls on the gap, and a reversed picture is shaped as an afterthought inverse to the opening. The natural eye acts particularly like a pin-gap camera.
Source of light:
An item that gives out light (luminous article) is known as a source of light.
Transparent material:
A material that transmits all the light is known as a transparent material.
Translucent material:
A material that transmits some measure of light is known as a translucent material.
Opaque material:
A material that totally obstructs the light is called an opaque material.
Shadow:
A region of haziness shaped by an opaque item hindering light is known as a shadow.
Objects can be transparent, translucent, or opaque, contingent upon how much light can go through them.
A shadow is framed when an opaque article hinders the light falling on it.
A shadow is consistently dark paying little heed to the shade of the item.
We state light is reflected when it bobs off a surface.
An unpleasant and rough surface reflects light in various ways.
A smooth surface reflects light just a single way.